Gas sensor device

Abstract

To provide a gas sensor device capable of accurately inspecting performance or a state of a member to be inspected by using an electrolytic gas pump even when a concentration of a gas is low and a current value is small.SOLUTION: A gas sensor device using electrolytic gas pumps P1, P3 capable of measuring a current flowing between a cathode 1 and an anode 2 is provided. The electrolytic gas pump P3 for gas exhaust is provided on a gas exhaust side of the electrolytic gas pump P1 for measurement, and a second chamber 20 on the gas exhaust side of the electrolytic gas pump P1 for measurement is communicated and connected with a first chamber 10 on a gas inflow side of the electrolytic gas pump P3 for gas exhaust, and the electrolytic gas pump P3 for gas exhaust exhausts a gas generated in the electrolytic gas pump P1 for measurement.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a gas sensor device that measures the performance, state, etc. of a predetermined member to be measured using an electrolytic gas pump.

Background Art

[0002] In recent years, barrier films (polymer films) have become indispensable not only for the long-term preservation of foods and pharmaceuticals but also for preventing deterioration of organic ELs and organic solar cells. In particular, oxygen causes spoilage and oxidative degradation, and it is necessary to shield it together with water. On the other hand, plastics (polymer films) are also related to environmental problems, and it is required from the perspective of SDGs to reduce the amount of use as much as possible and to make the films thinner and more functional. Thus, barrier films are an important base material and technology in a large hidden market, and it is expected that the demand will further expand in the future.

[0003] The gas permeability of such barrier films can be evaluated by a device having specifications according to individual requirements by users or conforming to standardization depending on the material. In particular, the manufacturing process of the material, the inspection of products, and the barrier properties under special conditions may be evaluated by a simple method and compared and verified with the evaluation by a standardized device, not limited to the standardized method. In particular, the products manufactured by Mocon, Inc. in the United States have high precision (oxygen transmission rate: OTR < 0.1 cc / m 2 / day / atm), but are expensive, and there is a demand for a device that can measure simply and inexpensively.

[0004] The present applicant has already proposed a device (electrolytic oxygen pump) for evaluating the oxygen transmission rate (OTR: Oxygen Transmission Rate, [cc / m 2 / day / atm]) from the current proportional to the amount of oxygen permeating through the barrier film by closing the reduction reaction electrode (cathode) side of the fuel cell with a barrier film (see, for example, Non-Patent Documents 1, 2, and Patent Document 1). In this method, when OTR > 100 cc / m 2The measurement limit of / day / atm is such that it is possible to measure high-density polyethylene (HDPE) with a thickness of 50 μm or less, for example. However, the actually required measurement sensitivity is for a hybrid film (OTR < 1 cc / m 2 / day / atm), and a device capable of clearing that sensitivity is required.

[0005] Here, FIG. 1 shows a device for measuring the oxygen transmission rate (OTR) of a barrier film F by an electrolytic oxygen pump P. The reduction reaction at the cathode 1 is such that, as shown by the following formula (1), O2 that has permeated through the barrier film is reduced by electrons (4e - ) supplied from the voltage application device 5 to become 4OH - and permeates through the separator 4 to the anode 2 side. The 4OH - that has permeated to the anode 2 side generates pure oxygen (O2) by an oxidation reaction according to the following formula (2). As the overall reaction, as shown by the following formula (3), O2 acts as an oxygen pump that moves from the cathode 1 to the anode 2. The H2O generated at the anode 2 permeates through the separator 4 and moves to the cathode 1 side, and the reduction reaction at the cathode 1 proceeds even without supplying H2O to the cathode 1. That is, when four electrons flow, it means that one O2 has been reduced. The cathode 1 and the anode 2 have the same reaction potential of 0.401 V with respect to the SHE, and if the polarization or IR drop at the electrode surface is compensated, the reaction occurs at a low potential.

[0006] <Reduction reaction at the cathode> 2H2O + O2 + 4e - → 4OH - 0.401 V vs.SHE …(1) <Oxidation reaction at the anode> 4OH - - 4e - → 2H2O + O2 0.401 V vs.SHE …(2) <Overall reaction> O2 (cathode) + 2H2O (cathode) → O2 (anode) + 2H2O (anode) 0V …(3)

[0007] The barrier film F of the device in Figure 1 is made of SUS plate, and the voltage application device 5 is V app When the current i is applied to both electrodes, a current i flows. At first, the oxygen in the cathode 1 is consumed by the reduction reaction, and the current decreases rapidly in about 30 minutes as shown in Figure 2(a). After that, the current decreases slowly, and after about 20 hours, the current value becomes the equilibrium current, that is, the level-off current (i ∞ ) and approaches a constant value. Like the current, the oxygen concentration in the first chamber 10 is initially 20% of atmospheric pressure but decreases to approximately 0.2%. Figure 2(b) shows the relationship between oxygen concentration and current value, which is almost a linear proportional relationship except for very low and very high concentrations. Even after more than 17 hours have passed since Figure 2(a), the current continues to flow slightly and does not become zero. The gas permeability coefficient of the SUS plate is nearly zero, and the level-off current should actually be zero, but it is a finite value. The behavior of the current decreasing while flowing slightly and the finite value are problematic, and it is important to investigate their origin.

[0008] Figure 3 shows the applied voltage (V app ) and level off current (i ∞ ) relationship. Particularly important results in Figure 3 are that there is a flat portion where the level-off current is independent of the applied voltage, and that a background current, shown by the dotted line, can be seen. The level-off current in the flat region is rate-limited by the amount of oxygen permeating the barrier film, ensuring that the oxygen permeability can be evaluated. In other words, this is only true for the level-off current, and indicates that this level-off current is in equilibrium with the amount of oxygen permeating the barrier film. Possible causes of the background current include (1) crossover of oxygen accumulated at the anode 2 to the cathode 1, (2) thermal excitation to the electrolysis potential of water, (3) oxygen adsorbed on the device housing or leakage from pinholes, or (4) injection of electrons or holes from the electrodes to the separator and electrolyte. Note that in Figure 3, the current values for HDPE 13 mm and Silicon 1.0 mm are smaller when the film area is 10 times larger (4 cm2). 2 →39cm 2 ) indicates that the level-off current will be approximately 10 times higher. [Prior art documents]

Non-Patent Literature

[0009]

Non-Patent Literature 1

Non-Patent Literature 2

Patent Literature

[0010]

Patent Literature 1

Summary of the Invention

Problems to be Solved by the Invention

[0011] As described above, when the oxygen transmission rate (OTR) of the barrier film is high (for example, OTR > 100 or more), measurement is generally possible. However, when the oxygen transmission rate (OTR) is low (for example, OTR < 10 or less), there has been a problem that it is difficult to measure the oxygen transmission rate (OTR) of the barrier film mainly due to the reasons (1) to (4) above. Such a problem also occurs similarly in the oxygen transmission rate of the measurement member other than the barrier film, and also occurs similarly in the electrolytic gas pump other than the oxygen pump (for example, the hydrogen pump). In addition, it is considered that the problem also occurs similarly in the measurement of the performance and state other than the oxygen transmission rate of the measurement member (for example, the measurement of the leakage of the sealed container). It is a problem derived from the overall measurement of the performance and state of the measurement member using the electrolytic gas pump.

[0012] The present invention has been made in view of the above problems, and an object of the present invention is to provide a gas sensor device capable of accurately measuring the performance and state of a measurement member using an electrolytic gas pump even when the gas concentration is low and the current value is small.

Means for Solving the Problem

[0013] In order to achieve the above object, the present invention includes a reduction reaction electrode disposed in a first chamber, an oxidation reaction electrode disposed in a second chamber, an electrolytic solution injected into the second chamber or the first chamber, an ion-exchangeable separator sandwiched between the reduction reaction electrode and the oxidation reaction electrode, and a voltage application device that applies a voltage to the reduction reaction electrode and the oxidation reaction electrode. The voltage application device applies a voltage to the reduction reaction electrode and the oxidation reaction electrode, and a gas flowing into the first chamber or the second chamber undergoes an electrochemical reduction reaction or an electrochemical oxidation reaction at one of the reduction reaction electrode or the oxidation reaction electrode, and at the same time, a gas generated by an electrochemical oxidation reaction or an electrochemical reduction reaction at the other oxidation reaction electrode or reduction reaction electrode is discharged from the second chamber or the first chamber. In this process, a gas sensor device using an electrolytic gas pump capable of measuring a current flowing between the oxidation reaction electrode and the reduction reaction electrode, wherein a discharge electrolytic gas pump is provided on the gas discharge side of the measurement electrolytic gas pump, and the second chamber or the first chamber on the gas discharge side of the measurement electrolytic gas pump is connected in communication with the first chamber or the second chamber on the gas inflow side of the discharge electrolytic gas pump, and the discharge electrolytic gas pump discharges the gas generated by the measurement electrolytic gas pump.

[0014] According to this, before or during the measurement of the member to be measured, the gas generated in one of the second chamber or the first chamber of the measurement electrolytic pump can be efficiently discharged, and thus the gas generated in one of the second chamber or the first chamber of the measurement electrolytic pump can be prevented from flowing back through the separator to the other first chamber or second chamber. Therefore, even when the gas concentration is low and the current value is small, it is possible to accurately measure the performance and state of the member to be measured using the electrolytic gas pump.

[0015] Further, it may include a holder that holds the member to be measured in a state where it is partitioned into a gas supply chamber and a gas permeation chamber by the member to be measured, an electrolytic gas pump for measurement disposed on the gas permeation chamber side in the holder, and an electrolytic gas pump for discharge disposed on the gas discharge side of the electrolytic gas pump for measurement. According to this, the gas permeability of the member to be measured can be accurately measured with a simple configuration.

[0016] Further, the holder may further include another electrolytic gas pump for discharge disposed on the gas supply chamber side. According to this, the gas in the gas supply chamber of the holder can be efficiently discharged before measuring the member to be measured, and the gas permeability of the member to be measured can be accurately measured when measuring the member to be measured.

[0017] Further, the holder may hold the member to be measured in a sandwiched state, and the opening area of the gas supply chamber may be formed larger than the opening area of the first chamber or the second chamber on the gas inflow side of the electrolytic gas pump for measurement. According to this, by forming the opening area of the gas supply chamber of the holder to be large, the gas permeation amount in the member to be measured can be increased, and the gas permeability of the member to be measured can be accurately measured.

[0018] The present invention also provides a gas sensor device using an electrolytic gas pump capable of measuring a current flowing between the oxidation reaction electrode and the reduction reaction electrode, the gas sensor device comprising: a reduction reaction electrode disposed in a first chamber; an oxidation reaction electrode disposed in a second chamber; an electrolytic solution injected into the second chamber or the first chamber; an ion-exchangeable separator sandwiched between the reduction reaction electrode and the oxidation reaction electrode; and a voltage application device for applying a voltage to the reduction reaction electrode and the oxidation reaction electrode. The voltage application device applies a voltage to the reduction reaction electrode and the oxidation reaction electrode, and a gas flowing into the first chamber or the second chamber undergoes an electrochemical reduction reaction or an electrochemical oxidation reaction at one of the reduction reaction electrode or the oxidation reaction electrode, while a gas generated by an electrochemical oxidation reaction or an electrochemical reduction reaction at the other oxidation reaction electrode or reduction reaction electrode is discharged from the second chamber or the first chamber. The voltage application device is characterized in that it applies an AC voltage having a predetermined frequency and amplitude superimposed on a DC voltage to the oxidation reaction electrode and the reduction reaction electrode. According to this, the current flowing between the oxidation reaction electrode and the reduction reaction electrode is stabilized and a so-called background current is reduced, so that even when the gas concentration is low and the current value is small, the performance and state of the member to be measured can be accurately measured.

[0019] The present invention also provides an electrolytic gas sensor device using an electrolytic gas pump capable of measuring a current flowing between a reduction reaction electrode disposed in a first chamber, an oxidation reaction electrode disposed in a second chamber, an electrolytic solution injected into the second chamber or the first chamber, an ion-exchangeable separator sandwiched between the reduction reaction electrode and the oxidation reaction electrode, and a voltage application device for applying a voltage to the reduction reaction electrode and the oxidation reaction electrode. The voltage application device applies a voltage to the reduction reaction electrode and the oxidation reaction electrode, and when the gas flowing into the first chamber or the second chamber undergoes an electrochemical reduction reaction or an electrochemical oxidation reaction at one of the reduction reaction electrode or the oxidation reaction electrode, and the gas generated by the electrochemical oxidation reaction or the electrochemical reduction reaction at the other oxidation reaction electrode or reduction reaction electrode is discharged from the second chamber or the first chamber, the device includes a holder that holds the member to be measured in a state where the member to be measured is partitioned into a gas supply chamber and a gas permeation chamber by the member to be measured, a measurement electrolytic gas pump connected to the gas permeation chamber via a first valve, and a reference electrolytic gas pump connected to the gas supply chamber via a second valve. When measuring, with the first valve closed and the second valve open, the current measured by the measurement electrolytic pump and the current measured by the reference electrolytic pump are differentially amplified. According to this, while measuring a current (Faraday current) in a state having a gas by the measurement electrolytic gas pump, a current (background current) in a state having no gas is measured by the reference electrolytic gas pump, and the voltage corresponding to the current (Faraday current) by the measurement electrolytic gas pump and the voltage for the current (background current) by the reference electrolytic gas pump are differentially amplified, so that the current obtained by removing the background current from the Faraday current corresponding to the gas can be accurately measured.

[0020] Further, the electrolytic gas pump for measurement and the electrolytic gas pump for reference may be symmetrically arranged in terms of position and configuration with respect to the member to be measured. According to this, it is possible to guarantee the current drift due to fluctuations in temperature and applied voltage.

[0021] Also, oxygen may be used as the gas. After hydroxide ions are generated by the electrochemical reduction reaction of oxygen at the reduction reaction electrode of the first chamber, the hydroxide ions permeate through the separator and move to the oxidation reaction electrode, and oxygen may be generated by the electrochemical oxidation reaction of the hydroxide ions at the oxidation reaction electrode of the second chamber. According to this, it is possible to accurately measure the performance, state, etc. of the member to be measured regarding oxygen.

[0022] Also, the current flowing between the oxidation reaction electrode and the reduction reaction electrode of the electrolytic pump may be measured, and the oxygen permeability of the member to be measured may be calculated by the following formula. According to this, it is possible to accurately measure the oxygen permeability of the member to be measured.

[0023] Oxygen Transmittance (OTR) = i ∞ V m / 4F / S / p i ∞ : Offset current V m : Molar volume of gas (oxygen) F: Faraday constant S: Area of the barrier film of the member to be measured p: Pressure difference of gas (oxygen)

[0024] Also, the member to be measured may be a barrier film used for packaging materials. According to this, it is possible to accurately measure the oxygen permeability of the barrier film.

[0025] The member to be measured may be a sealed container. According to this, it is possible to accurately measure the performance, state, etc. such as leakage of the sealed container.

Advantages of the Invention

[0026] According to the present invention, before or during the measurement of the member to be measured, the gas generated in one of the second chambers or the first chamber of the electrolytic pump for measurement can be efficiently discharged. As a result, it is possible to prevent the gas generated in one of the second chambers or the first chamber of the electrolytic pump for measurement from passing through the separator and flowing back to the other first chamber or second chamber. Therefore, even when the gas concentration is low and the current value is small, it is possible to accurately measure the performance and state of the member to be measured using the electrolytic gas pump.

Brief Description of the Drawings

[0027]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Embodiment for Carrying Out the Invention

[0028] Next, an embodiment of the gas sensor device according to the present invention (hereinafter referred to as this device) will be described. In this device, the case where the oxygen transmission rate (OTR) of the barrier film F as the member to be measured is measured using an electrolytic oxygen pump in which oxygen is used as the gas will be described.

[0029] <Basic Principle of Electrolytic Oxygen Pump P> First, the basic principle of the electrolytic oxygen pump P will be described with reference to FIG. 1.

[0030] As shown in FIG. 1(a), the electrolytic oxygen pump P includes a reduction reaction electrode (hereinafter referred to as cathode 1) disposed in the first chamber 10, an oxidation reaction electrode (hereinafter referred to as anode 2) disposed in the second chamber 20, an electrolytic solution 3 injected into the second chamber 20, an ion-exchangeable separator 4 sandwiched between the cathode 1 and the anode 2, and a voltage application device 5 that applies a voltage to the cathode 1 and the anode 2.

[0031] As the material of the cathode 1, for example, nickel sponge is preferably used, but other materials may be used. On the other hand, for the anode 2, a conductive material such as a carbon sheet is preferably used, and it preferably contains a catalyst (for example, platinum Pt) so that the reaction proceeds smoothly. Further, the separator 4 functions as a permeation membrane that delivers ions generated at one of the cathode 1 or the anode 2 to the other anode 2 or cathode 1.

[0032] When an alkaline electrolytic solution is used as the electrolytic solution 3, the following formula (1) is for the cathode 1 where an electrochemical reduction reaction (hereinafter referred to as a reduction reaction) occurs, the following formula (2) is for the anode 2 of the electrochemical oxidation reaction (hereinafter referred to as an oxidation reaction), and the overall reaction is shown by the following formula (3).

[0033] <Reduction Reaction at the Cathode> 2H2O + O2+ 4e - → 4OH - 0.401V vs. SHE …(1)

[0034] <Oxidation Reaction at the Anode> 4OH - - 4e - → 2H2O + O2 0.401V vs. SHE …(2)

[0035] <Overall Reaction> O2 (cathode) + 2H2O (cathode) → O2 (anode) + 2H2O (anode) 0V …(3)

[0036] The reaction potential is the potential with respect to the hydrogen standard electrode (SHE: Standard Hydrogen Electrode), and the reaction occurs at the same potential at the cathode 1 and the anode 2. However, in order to induce the oxidation-reduction reaction and further compensate for the potential drop due to the contact resistance with the electrode, a voltage V app needs to be applied from the voltage application device 5.

[0037] Here, at the cathode 1, O2 and 2H2O that have permeated through the barrier film F are reduced by 4e - according to the above formula (1) to become 4OH - and move to the anode 2 by the electric field through the separator 4. At the anode 2, 4OH - is oxidized to generate O2 and 2H2O. Since O2 is hardly soluble in water, it is released as pure O2. The voltage V app is the potential energy required for O2 and H2O to add electrons and be reduced on the catalyst surface, and similarly for OH - to release electrons and be oxidized. Catalysis is to reduce these potential energies. The 2H2O at the cathode 1 is automatically replenished by the H2O generated at the anode 2 diffusing through the separator 4 and permeating to the anode 2 side. Here, since a cellulose dialysis membrane is used for the separator 4, it swells with water, and OH - hydrates and moves. This OH -is also necessary for moving app The current i flowing through the external circuit in Fig. 1 is called the Faraday current, which is derived from positive and negative ions generated by oxidation and reduction. The Faraday current (i = C / s) is such that one O2 is reduced for a charge of 4e - , so the amount of oxygen reduced from the current i can be determined. That is, when the cathode 1 is blocked by the barrier film F with an area (S), the current decays and reaches an equilibrium state (level-off current i ∞ ) after a sufficiently long time. Therefore, the oxygen transmission rate (OTR) of the barrier film F can be determined from the level-off current i ∞ .

[0038] Silicon rubber plates with thicknesses of 0.1 mm and 1.0 mm and an area S = 4 cm 2 are used as the barrier film F, and the time variation of the Faraday current of the electrolytic oxygen pump is shown in Fig. 4. The current reaches the level-off current i ∞ in a few minutes. Since the level-off current i ∞ is inversely proportional to the thickness of the barrier film F, naturally the amount of O2 permeation decreases inversely proportional to the thickness of the barrier film F. Since the 0.1 mm SUS plate hardly permeates O2, the level-off current i ∞ should originally be 0. However, due to the reasons described in the prior art, it does not become 0 and is related to the measurement limit of the permeation rate. In order to evaluate the oxygen permeation rate (OTR) from the level-off current i ∞ , it is a condition that the level-off current i ∞ is rate-determined by the amount of oxygen permeating through the barrier film F. This can be confirmed by the existence of a region where the level-off current i ∞ does not depend on the voltage V app . The oxygen permeation rate (OTR) of the barrier film F can be obtained from the following equation (4) from the level-off current i ∞ obtained under the above conditions.

[0039] OTR = i ∞ V m / 4F / S / p (cc / m 2 / day / atm)…(4)

[0040] Note that i ∞ is converted from the unit of C / S to day and is 8.64×10 4 C / day, V m is the molar volume of oxygen (cc / mol), F is the Faraday constant, S is the area of the barrier film (m 2 ), and p is the pressure difference of oxygen (atm) before and after the barrier film F (the gas supply chamber 101 and the gas permeation chamber 102 described later).

[0041] In this way, in the electrolytic oxygen pump P, the voltage application device 5 applies a voltage to the cathode 1 (reduction reaction electrode) and the anode 2 (oxidation reaction electrode), and the oxygen (O2) flowing into the first chamber 10 is reduced at the cathode 1. At the same time, in the process where the oxygen (O2) generated by the oxidation reaction at the other anode 2 is discharged from the second chamber 20, the oxygen transmission rate (OTR) can be measured by measuring the current flowing between the cathode 1 and the anode 2. As shown in Fig. 1(b), overall, oxygen flows into and is discharged from the device.

[0042] <First Embodiment> Next, the first embodiment of the present device will be described with reference to Figs. 5 and 6.

[0043] As shown in Fig. 5, the present device includes a holder 100 that holds a barrier film F as a member to be measured, a measurement electrolytic oxygen pump P1 disposed on one side (the left side in Fig. 5) of the barrier film F in the holder 100, a discharge electrolytic oxygen pump P2 disposed on the other side (the right side in Fig. 5) of the barrier film F in the holder 100, and a discharge electrolytic oxygen pump P3 disposed on the gas outflow side of the measurement electrolytic oxygen pump P1.

[0044] The holder 100 holds both sides of the barrier film F in a sandwiched state via O-rings. A gas supply chamber 101 is defined on one side of the barrier film F (the right side in FIG. 5), and a gas permeation chamber 102 is defined on the other side of the barrier film F (the left side in FIG. 5) in a sealed state. Further, this holder 100 is connected to a piezo pump and an oxygen supply device (100% O2 balloon) via valves V1 and V2. Oxygen concentration meters are provided in the gas supply chamber 101 and the gas permeation chamber 102 of the holder 100, respectively.

[0045] The electrolytic oxygen pump P1 for measurement has the same configuration as the electrolytic oxygen pump P (excluding the barrier film F) shown in FIG. 1 and is an electrolytic oxygen pump for measuring the oxygen transmission rate (OTR) of the barrier film F. The first chamber 10 on the gas inflow side is connected to the gas permeation chamber 102 of the holder 100 in a communicating state, and the second chamber 20 on the gas outflow side is connected to the first chamber 10 on the gas inflow side of the electrolytic oxygen pump P3 for discharge outside the device in a communicating state.

[0046] The electrolytic oxygen pump P2 for discharge also has the same configuration as the electrolytic oxygen pump (excluding the barrier film F) shown in FIG. 1 and is an electrolytic oxygen pump for discharging oxygen. The first chamber 10 on the gas inflow side is connected to the gas supply chamber 101 of the holder 100 in a communicating state, and the second chamber 20 on the gas outflow side is connected to the oxygen supply device (100% O2 balloon) in a communicating state. Note that the electrolytic oxygen pump P2 for discharge does not necessarily need to measure current.

[0047] The electrolytic oxygen pump P3 for discharge also has the same configuration as the electrolytic oxygen pump (excluding the barrier film F) shown in FIG. 1 and is an electrolytic oxygen pump for discharging gas. The first chamber 10 on the gas inflow side is connected to the second chamber 20 on the gas discharge side of the electrolytic oxygen pump P1 for measurement outside the device in a communicating state. Note that the electrolytic oxygen pump P3 for discharge does not necessarily need to measure current.

[0048] Before measuring the oxygen transmission rate (OTR) of the barrier film F, when the electrolytic oxygen pump P1 for measurement is operated with the valves V1 and V2 closed, oxygen in the gas permeation chamber 102 of the holder 100 and oxygen contained in the barrier film F flow into the first chamber 10 of the electrolytic oxygen pump P1 for measurement, and the oxygen generated in the second chamber 20 is discharged outside the apparatus. Therefore, the oxygen (atmosphere) in the gas permeation chamber 102 of the holder 100 can be degassed.

[0049] Also, before measuring the oxygen transmission rate (OTR) of the barrier film F, when the electrolytic oxygen pump P2 for discharge is operated in the same state with the valves V1 and V2 closed, oxygen in the gas supply chamber 101 of the holder 100 flows into the first chamber 10, and the oxygen generated in the second chamber 20 is discharged to the oxygen supply device side. Therefore, the oxygen (atmosphere) in the gas supply chamber 101 of the holder 100 can be degassed.

[0050] Also, when measuring the oxygen transmission rate (OTR) of the barrier film F, when the electrolytic oxygen pump P1 for measurement is operated in a state where oxygen is supplied from the oxygen supply device into the gas supply chamber 101 of the holder 100, as time passes, oxygen that has permeated from the gas supply chamber 101 through the barrier film F into the gas permeation chamber 102 flows into the first chamber 10, and the oxygen generated from the second chamber 20 is discharged to the outside. At this time, as described in the <basic principle of the oxygen electrolytic pump> above, the oxygen transmission rate (OTR) of the barrier film F can be measured by measuring the current flowing between the cathode 1 and the anode 2 with the electrolytic oxygen pump P1 for measurement.

[0051] Furthermore, before and during the measurement of the oxygen transmission rate (OTR) of the barrier film F, when the electrolytic oxygen pump P3 for discharge is operated, the oxygen discharged from the second chamber 20 of the electrolytic oxygen pump P1 for measurement flows into the first chamber 10 of the electrolytic oxygen pump P3 for discharge, and the oxygen generated in the second chamber 20 of the electrolytic oxygen pump P3 for discharge is discharged outside the apparatus. As a result, the oxygen generated by the electrolytic oxygen pump P1 for measurement can be efficiently discharged. Consequently, it is possible to prevent oxygen from flowing back from the second chamber 20 to the first chamber 10 in the electrolytic oxygen pump P1 for measurement, and it becomes possible to accurately measure the performance and state of the barrier film F using the electrolytic gas pump P1 for measurement.

[0052] [Verification Experiment of the Present Apparatus in the First Embodiment] Using an apparatus equivalent to the one shown in FIG. 5, the oxygen transmission rate (OTR) of a barrier film F of TOYOBO E5100 PET (12 μm) was measured. FIG. 6 shows an example of the measurement of the oxygen transmission rate (OTR). In this example, since the electrolytic oxygen pump P2 for discharge on the gas supply chamber 101 side was not operated, the initial oxygen concentration in the gas supply chamber 101 was 20% in the atmosphere. FIG. 6(a) shows the degassing process, and FIG. 6(b) shows the time response of the current flowing through the electrolytic oxygen pump P1 for measurement when 80% oxygen was supplied to the oxygen supply chamber after degassing was completed. It was found that the current value (i ∞ ) changed by 51 μA due to a change in oxygen concentration of 60%. The oxygen transmission rate (OTR) (cc / m 2 / day / atm) is obtained by the above formula (4).

[0053] Substituting i ∞ = 51 μA into the above formula (4), and since an O-ring with a diameter of 70 mm was used for S, S = 39×10 -4 m 2 , and p = 0.6 atm, OTR = 110 cc / m 2 / day / atm was obtained. This value is almost the same as the OTR = 120 published by TOYOBO.

[0054] From the above, at least a barrier film F with OTR > 10 can be currently evaluated. In particular, from FIG. 6(b), it can be confirmed that the change in the level-off current i ∞ is due to the change in the oxygen concentration in the oxygen supply chamber 101. Also, an improvement in sensitivity can be expected by further reducing the background current, such as in a tandem method using the electrolytic oxygen pump P3 for discharge.

[0055] <Second Embodiment> Next, a second embodiment of the present apparatus will be described with reference to FIGS. 7 and 8. Hereinafter, only the configurations different from the above embodiment will be described, and the same configurations will be omitted and denoted by the same reference numerals.

[0056] As shown in FIG. 7, the present apparatus includes a holder 100 that holds a barrier film F as a member to be measured, and an electrolytic oxygen pump P1 for gas measurement disposed on one side (the lower side in FIG. 7) of the barrier film F in the holder 100.

[0057] The holder 100 holds both sides of the barrier film F in a sandwiched state, and a gas supply chamber 101 is defined in a sealed state on one side (the upper side in FIG. 7) of the barrier film F, and a gas permeation chamber 102 is defined in a sealed state on the other side (the lower side in FIG. 7) of the barrier film F. Further, the holder 100 is connected to an oxygen supply device (O2Gas) and a nitrogen supply device (N2Gas) via a valve, and is also connected to a diaphragm pump. In addition, verification oxygen concentration meters (O2monitor) for measuring the oxygen concentration and temperature are provided in the gas supply chamber 101 and the gas permeation chamber 102, respectively.

[0058] The electrolytic oxygen pump P1 for measurement has the same configuration as the electrolytic oxygen pump shown in FIG. 1 (excluding the barrier film F), and is an electrolytic oxygen pump for measuring the oxygen transmission rate (OTR) of the barrier film F. The first chamber 10 on the gas inflow side is connected in communication with the gas supply chamber 101 of the holder 100. The superimposed AC voltage is, for example, in the range of frequency f = 10 to 100 kHz, amplitude V pp = 1 mV to 1 V, and the bias voltage (offset) V offset = 0.1 to 1.2 V is preferably used.

[0059] Also, in the electrolytic pump P1 for measurement, the voltage application device 5 superimposes an AC voltage of a predetermined frequency and amplitude on the cathode 1 and the anode 2 and applies it. According to this, the current flowing between the cathode 1 and the anode 2 is stabilized, and the so-called background current is reduced. Therefore, even when the oxygen concentration is low and the current value is small, the oxygen transmission rate (OTR) of the barrier film can be accurately measured.

[0060] Thus, when measuring the oxygen transmission rate (OTR) of the gas barrier film F, when the electrolytic oxygen pump P1 for measurement is operated in a state where oxygen is supplied from the oxygen supply device into the gas supply chamber 101 of the holder 100, oxygen that has permeated from the gas supply chamber 101 through the barrier film F into the gas permeation chamber 102 flows into the first chamber 10 over time, and oxygen generated from the second chamber 20 is discharged to the outside. At this time, as described in the <basic principle of the electrolytic oxygen pump P> above, the oxygen transmission rate (OTR) of the barrier film F can be accurately measured by measuring the current flowing between the cathode 1 and the anode 2 with the gas electrolytic oxygen pump P1 for measurement.

[0061] [Verification Experiment of the Apparatus of the Second Embodiment] In the measurement example of FIG. 2(b), the current response to the oxygen pressure change (20% to 80% = 60%) of the barrier film F is not clear. Therefore, the apparatus is configured as shown in FIG. 7, and an AC voltage (V pp) superimposed voltage E0 (V of the arbitrary function generator offset ) was applied to stabilize the current. Here, V offset = 0.7 V, frequency f = 200 Hz, amplitude of the AC voltage (V pp = 50 mV). Therefore, by supplying air or purging with N2 gas to the oxygen supply chamber 101, the oxygen concentration was changed by 0.2 atm, and the current change at that time was measured. Regarding the reason why the signal is stabilized by superimposing the AC voltage, (1) the interfacial polarization of positive and negative ions in the electrolyte 3 can be suppressed, and (2) the dipole polarization current of water can be pinned, etc. are considered.

[0062] The current change in Fig. 8(a) is about 6 μA and the oxygen pressure difference is different, but it is about one-third of the directly obtained current value. The reason for this difference in current values is not clear, but it can be treated as a correction factor. Another experimental result measured under different conditions is shown in Fig. 8(b). Of particular note is that when the current value becomes small, the tandem-type device of the present apparatus shown in Fig. 5 of the first embodiment exerts its power, and the stabilization of the current and the reduction of the background current can be expected to be effective.

[0063] <The Third Embodiment> Next, the third embodiment of the present apparatus will be described with reference to Fig. 9. In the following, only the configurations different from the above embodiments will be described, and the description of the same configurations will be omitted and the same reference numerals will be given.

[0064] As shown in Fig. 9(a), this device includes a holder 100 that holds a barrier film F as a member to be measured, an electrolytic oxygen pump P1 for measurement disposed on one side (the lower side in Fig. 9) of the barrier film F in the holder 100, a reference electrolytic oxygen pump P4 disposed on one side (the upper side in Fig. 9) of the barrier film F in the holder 100, and, as shown in Fig. 9(b), a discharge electrolytic oxygen pump P3 disposed on the gas outflow sides of the electrolytic oxygen pump P1 for measurement and the reference electrolytic oxygen pump P4. Note that the electrolytic oxygen pump P1 for measurement and the reference electrolytic oxygen pump P4 are symmetrically arranged with respect to both the position and configuration (valves and diaphragms) with respect to the barrier film F of the holder 100, and the same voltage is applied before and during the measurement of the oxygen transmission rate (OTR) of the barrier film F.

[0065] The holder 100 holds the barrier film F in a sandwiched state, and a gas supply chamber 101 is defined in a sealed state on one side (the upper side in Fig. 9) of the barrier film F, and a gas permeation chamber 102 is defined in a sealed state on the other side (the lower side in Fig. 9) of the barrier film F. Further, the holder 100 is connected to an oxygen supply device (O2Gas) and a nitrogen supply device (N2Gas) via valves in the gas supply chamber 101. Note that verification oxygen concentration meters (O2monitor) for measuring the oxygen concentration and temperature are provided in the gas supply chamber 101 and the gas permeation chamber 102, respectively.

[0066] The electrolytic oxygen pump P1 for measurement has the same configuration as the electrolytic oxygen pump shown in Fig. 1 (excluding the barrier film F). As shown in Fig. 9(a), the first chamber 10 on the gas inflow side is connected in a communicating state to the gas permeation chamber 102 of the holder 100 via valves V1, V2 (the first valve) and a diaphragm pump (Daiaphram Pump).

[0067] The reference electrolytic oxygen pump P4 has the same configuration as the electrolytic oxygen pump shown in FIG. 1 (excluding the barrier film F). As shown in FIG. 9(a), the first chamber 10 on the gas inflow side is connected in communication with the gas supply chamber 101 of the holder 100 via valves V3, V4 (the second valve) and a diaphragm pump.

[0068] The discharge electrolytic oxygen pump P3 has the same configuration as the electrolytic oxygen pump shown in FIG. 1 (excluding the barrier film F). As shown in FIG. 9(b), the first chamber 10 on the gas inflow side is connected to the second chamber 20 on the gas outflow side of the measuring electrolytic oxygen pump P1 and the second chamber 20 of the reference electrolytic oxygen pump P4.

[0069] Thus, before measuring the oxygen transmission rate (OTR) of the barrier film F, when the measuring electrolytic oxygen pump P1 and the reference electrolytic oxygen pump P4 are operated with valves V1 to V4 open, the oxygen in the apparatus is degassed.

[0070] Also, when measuring the oxygen transmission rate (OTR) of the barrier film F, the reference electrolytic oxygen pump P4 is operated with valves V3 and V4 closed. As described in the <basic principle of the electrolytic oxygen pump P> above, the current flowing between the cathode 1 and the anode 2 in the reference electrolytic oxygen pump (the bag ground current in the state without oxygen: BCG) is measured by the voltage V R thereby.

[0071] Also, when measuring the oxygen transmission rate (OTR) of the barrier film F, when oxygen is supplied from the oxygen supply device into the gas supply chamber 101 of the holder 100, in the holder 100, the barrier film F permeates from the gas supply chamber 101 toward the gas permeation chamber 102 over time. Then, when the electrolytic oxygen pump P1 for measurement is operated with the valves V1 and V2 open, as described in the <basic principle of the electrolytic oxygen pump P> above, the current flowing between the cathode 1 and the anode 2 in the electrolytic oxygen pump P1 for measurement (Faraday current corresponding to the oxygen in the gas permeation chamber 102 that has permeated through the barrier film F) is measured by the voltage V S Thereby measured.

[0072] Also, the voltage V measured by the electrolytic oxygen pump P1 for measurement S and the voltage V measured by the reference electrolytic oxygen pump P4 R are input into the subtraction circuit shown in FIG. 9(c) and differentially amplified to extract only the current of oxygen that has permeated through the barrier film F, and the current obtained by removing the bag ground current from the Faraday current can be accurately measured. Moreover, as described above, the electrolytic oxygen pump P1 for measurement and the reference electrolytic oxygen pump P4 are arranged symmetrically in close proximity, and by applying the same voltage, it is possible to compensate for the current drift due to temperature changes and fluctuations in the applied voltage.

Example

[0073] Next, an example of the specific configuration of this apparatus for measuring the oxygen transmission rate (OTR) of the barrier film F will be described with reference to FIGS. 10 and 11.

[0074] As shown in FIG. 10, this apparatus comprises an electrolytic oxygen pump P1 for measurement of the oxygen transmission rate (OTR) of the barrier film F and a holder 100 for holding the barrier film F, and these electrolytic oxygen pump P1 and holder 100 are integrally configured.

[0075] The electrolytic oxygen pump P1 for measurement is composed of a first chamber 10 from the holder 100 side (the right side in FIG. 10), a member corresponding to the cathode 1 (Current collector SUS316 plate 0.1mm / cathode Pt-catalyst / Florine gasket), an ion-exchangeable separator 4 (Separator), a member corresponding to the anode 2 (Florine gasket / Anode Ni sponge / Current collector SUS316 plate 0.1mm), and a second chamber 20 (into which the electrolyte KOH / H2O is injected). A voltage application device 5 (not shown) applies a voltage to the anode 1 and the cathode 2.

[0076] As shown in FIGS. 10 and 11, the holder 100 is composed of two acrylic members corresponding to a gas supply chamber 101 and a gas permeation chamber 102, and holds a barrier film F (Barrier film) in a sandwiched state via an O-ring (O-ring). An oxygen monitor port (O2Monitor port) is provided in the gas permeation chamber 102 of the holder 100, and the oxygen concentration for verification can be directly confirmed by an oxygen concentration meter (not shown).

[0077] Also, since the opening area (inner diameter 70 mm) of the opening (Air Inret) of the gas supply chamber 101 to which oxygen is supplied in the holder 100 is formed larger than the opening areas of the plurality of openings of the first chamber 10 of the electrolytic oxygen pump P1, the oxygen permeation area in the barrier film F becomes larger, the oxygen permeation amount can be increased, and the oxygen transmission rate (OTR) of the barrier film F can be accurately measured.

[0078] In each of the above embodiments, the oxygen transmission rate (OTR) of the barrier film F is measured. However, other performances and states related to oxygen of other members to be measured may also be measured. For example, it includes measuring the quantitative leakage of sealed containers such as paper packs, plastic containers, and metal containers. In this case, p in the above formula (4) is the pressure (atm) of oxygen outside the container.

[0079] Also, although oxygen is used as the gas, other gases such as hydrogen may be used. In this case, while the gas flowing into the second chamber 20 undergoes an electrochemical oxidation reaction at the anode 2, the current flowing between the cathode 1 and the anode 2 may be measured in the process where the gas generated by the electrochemical reduction reaction at the cathode 1 is discharged from the first chamber 10.

[0080] In addition, although the case where an alkaline electrolyte is used as the electrolyte (the above formulas (1) to (3)) has been described, it is also possible to use an acidic electrolyte. In this case, at the cathode 1 where the reduction reaction occurs, the following formula (5) applies, at the anode 2 of the oxidation reaction, the following formula (6) applies, and the overall reaction is shown by the following formula (7).

[0081] <Reduction reaction at the cathode> O2 + 4H + + 4e - → 2H2O 1.229V vs.SHE …(5)

[0082] <Oxidation reaction at the anode> 2H2O - 4e - → 4H + +O2 1.229V vs.SHE …(6)

[0083] <Overall reaction> O2 (cathode) + 2H2O (anode) → O2 (anode) + 2H2O (cathode) 0V …(7)

[0084] As described above, the embodiments of the present invention have been described with reference to the drawings, but the present invention is not limited to the illustrated embodiments. Various modifications and variations can be made within the same scope or the equivalent scope of the present invention with respect to the illustrated embodiments.

Explanation of reference numerals

[0085] 1…Cathode 2…Anode 3…Electrolyte 4…Separator 5…Voltage application device 10…First chamber 20…Second chamber 100…Holder 101…Gas supply chamber 102…Gas permeation chamber P1…Electrochemical oxygen pump for measurement P2…Electrochemical oxygen pump for discharge P3…Electrochemical oxygen pump for discharge P4…Electrochemical oxygen pump for reference

Claims

1. A reduction reaction electrode disposed in a first chamber, an oxidation reaction electrode disposed in a second chamber, an electrolytic solution injected into the second chamber or the first chamber, an ion-exchangeable separator sandwiched between the reduction reaction electrode and the oxidation reaction electrode, and a voltage application device for applying a voltage to the reduction reaction electrode and the oxidation reaction electrode, wherein the voltage application device applies a voltage to the reduction reaction electrode and the oxidation reaction electrode, and a gas flowing into the first chamber or the second chamber undergoes an electrochemical reduction reaction or an electrochemical oxidation reaction at one of the reduction reaction electrode or the oxidation reaction electrode, and a gas generated by an electrochemical oxidation reaction or an electrochemical reduction reaction at the other oxidation reaction electrode or reduction reaction electrode is discharged from the second chamber or the first chamber. A gas sensor device using an electrolytic gas pump capable of measuring a current flowing between the oxidation reaction electrode and the reduction reaction electrode, wherein a discharge electrolytic gas pump is provided on the gas discharge side of the electrolytic gas pump for measurement, wherein the second chamber or the first chamber on the gas discharge side of the electrolytic gas pump for measurement is connected in communication with the first chamber or the second chamber on the gas inflow side of the discharge electrolytic gas pump, and the discharge electrolytic gas pump discharges the gas generated by the electrolytic gas pump for measurement. A gas sensor device characterized by this.

2. A holder for holding the member to be measured in a state where it is partitioned into a gas supply chamber and a gas permeation chamber by the member to be measured, the electrolytic gas pump for measurement disposed on the gas permeation chamber side in the holder, and the discharge electrolytic gas pump disposed on the gas discharge side of the electrolytic gas pump for measurement. The gas sensor device according to claim 1.

3. The gas sensor device according to claim 2, wherein the holder further includes another discharge electrolytic gas pump disposed on the gas supply chamber side.

4. The gas sensor device according to claim 2, wherein the holder holds the member to be measured in a sandwiched state, and the opening area of the gas supply chamber is formed larger than the opening area of the first chamber or the second chamber on the gas inflow side of the electrolytic gas pump for measurement.

5. A reduction reaction electrode disposed in the first chamber, an oxidation reaction electrode disposed in the second chamber, an electrolytic solution injected into the second chamber or the first chamber, an ion-exchangeable separator sandwiched between the reduction reaction electrode and the oxidation reaction electrode, and a voltage application device that applies a voltage to the reduction reaction electrode and the oxidation reaction electrode. A gas sensor device using an electrolytic gas pump capable of measuring a current flowing between the oxidation reaction electrode and the reduction reaction electrode in a process where the voltage application device applies a voltage to the reduction reaction electrode and the oxidation reaction electrode, and a gas flowing into the first chamber or the second chamber undergoes an electrochemical reduction reaction or an electrochemical oxidation reaction at one of the reduction reaction electrode or the oxidation reaction electrode, and a gas generated by an electrochemical oxidation reaction or an electrochemical reduction reaction at the other oxidation reaction electrode or reduction reaction electrode is discharged from the second chamber or the first chamber. The gas sensor device is characterized in that the voltage application device applies an AC voltage having a predetermined frequency and amplitude superimposed on a DC voltage to the oxidation reaction electrode and the reduction reaction electrode.

6. A reduction reaction electrode disposed in the first chamber, an oxidation reaction electrode disposed in the second chamber, an electrolytic solution injected into the second chamber or the first chamber, an ion-exchangeable separator sandwiched between the reduction reaction electrode and the oxidation reaction electrode, and a voltage application device that applies a voltage to the reduction reaction electrode and the oxidation reaction electrode. A gas sensor device using an electrolytic gas pump capable of measuring a current flowing between the oxidation reaction electrode and the reduction reaction electrode in a process where the voltage application device applies a voltage to the reduction reaction electrode and the oxidation reaction electrode, and a gas flowing into the first chamber or the second chamber undergoes an electrochemical reduction reaction or an electrochemical oxidation reaction at one of the reduction reaction electrode or the oxidation reaction electrode, and a gas generated by an electrochemical oxidation reaction or an electrochemical reduction reaction at the other oxidation reaction electrode or reduction reaction electrode is discharged from the second chamber or the first chamber. A holder that holds the member to be measured in a state where the member to be measured divides the gas supply chamber and the gas permeation chamber, a measurement electrolytic gas pump connected to the gas permeation chamber via a first valve, and a reference electrolytic gas pump connected to the gas supply chamber via a second valve. A gas sensor device characterized in that, when measuring, with the first valve closed and the second valve open, the current measured by the measurement electrolytic pump and the current measured by the reference electrolytic pump are differentially amplified.

7. The gas sensor device according to claim 6, wherein the measurement electrolytic gas pump and the reference electrolytic gas pump are symmetrically arranged in terms of position and configuration with respect to the member to be measured.

8. Oxygen is used as the gas. After hydroxide ions are generated by the electrochemical reduction reaction of oxygen at the reduction reaction electrode of the first chamber, the hydroxide ions permeate through the separator and move to the oxidation reaction electrode, and oxygen is generated by the electrochemical oxidation reaction of the hydroxide ions at the oxidation reaction electrode of the second chamber. The gas sensor device according to any one of claims 1 to 7.

9. The gas sensor device according to claim 8, wherein the current flowing between the oxidation reaction electrode and the reduction reaction electrode of the electrolytic pump is measured, and the oxygen permeability of the member to be measured is calculated by the following formula. Oxygen permeability (OTR) = i ∞ V ｍ / 4F / S / p i ∞ : Level-off current V ｍ : Molar volume of gas (oxygen) F: Faraday constant S: Area of the member to be measured p: Pressure difference of the gas (oxygen)

10. The gas sensor device according to claim 9, wherein the member to be measured is a barrier film used for a packaging material.

11. The gas sensor device according to claim 9, wherein the member to be measured is a sealed container.

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